Donald Sterling said he will look into Adam Silver and David Stern's salary over the years. (AP Photo/Wilfredo Lee)

Los Angeles Clippers owner Donald Sterling and his lawyers hired four private investigation firms to dig up "dirt" on former NBA commissioner David Stern, current commissioner Adam Silver and the league's 29 other owners, reports the Associated Press.

The investigators were given a six-figure budget to look into the league's finances, find allegations of previous discriminatory conduct, and compensation to Stern and Silver, according to the report.

"The gloves are off, as they say," according to a person who spoke on the condition of anonymity. "Have them dig up all the dirt they can find."

Sterling is suing the NBA for $1 billion after the league fined him $2.5 million and banned him for life over him making recorded racist remarks that were later leaked publicly.

He says the league violated his constitutional rights, committed a breach of contract, and violated antitrust laws by trying to strip the Clippers' ownership from him and force the sell of the team.

Sterling's attorneys will also face off with his wife, Shelly Sterling, during a four-day hearing in probate court scheduled to start July 7. The hearing will focus on whether Shelly Sterling had the right to broker a $2 billion deal to sell the team to former Microsoft executive Steve Ballmer.

More from the AP:

The person who spoke to the AP said Donald Sterling reluctantly agreed to hire private investigators after this week's legal proceedings in probate court. The NBA submitted a legal filing Wednesday urging a judge to confirm Shelly Sterling's authority to sell the team.

"He realized these guys will literally go to any low to get this sold," the person said. "Even if it gets (him) nothing other than exposing all these guys and shaking up the league and seeing a change in the leadership of the league, it'll be worth it to him."